Electrical precipitator voltage control



Feb. 26, 1957 H. A. WINTERMUTE 2,783,388

ELECTRICAL PRECIPITATOR VOLTAGE CONTROL Filed Aug. 24, 1954- 2Sheets-Sheet 1 INVENTOR HARRY WINTERMUTE ATTORNEY Feb. 26, 1957 H. A.WINTERMUTE 2,783,388

ELECTRICAL PRECIPITATOR VOLTAGE CONTROL Filed Aug. 24, 1954 2Sheets-Sheet 2.

HARRY A. WlNTERMUTE MTW BY ATTORNEY United States Patent ELECTRICALPRECIPITATOR VOLTAGE CONTROL Harry A. Wintermute, Plainfield, N. J.,assignor to Research Corporation, New York, N. Y., a corporation of NewYork Application August 24, 1954, Serial No. 451,770

5 Claims. (Cl. 250-83.6)

This invention relates to a voltage regulating system for an electricalprecipitator, and more particularly to a system for controlling orregulating the voltage applied to the electrodes of a high voltageprecipitator so as to produce an optimum rate of sparking or arcingduring precipitator operation.

It is well known that the most efiicient precipitator operation occurswhen the precipitator is sparking or arcing at some definite rate, whichwill depend in any given case upon a number of conditions, such asnature and type of material being treated, physical parameters of thesystem, etc. However, for any given precipitator and given set ofoperating conditions, there is an optimum rate of sparking. Precipitatorcontrol systems are known for maintaining the optimum sparking rate inaccordance with the integrated value of the actual sparking rate, forexample, as shown in U. S. Patent No. 2,623,608 to Herbert J. Hall.

It is a primary object of the invention to regulate the operatingvoltage of an electrical precipitator as a function of the sparkingrate, in order to maintain an optimum or predetermined arcing rate.

High voltage industrial precipitators generally employ a step-uptransformer for producing the desired high voltage, in conjunction withrectifier means on the high voltage side in order to provide a definitepolarity of D.-C. voltage to the precipitator electrodes, as is requiredfor best operation. Mechanical rectifiershave often been used for thispurpose in the past, but the tendency in modern systems is to employhigh voltage electronic rectifiers, such as the well-known kenotrontubes which are commercially available for this purpose. The kenotron isa high-voltage diode built primarily to serve as a rectifier, but is, inits essential construction, also very similar to an X-ray generator.While the kenotron is ordinarily designed for operation at voltagessufiiciently low so that no appreciable amount of X-rays are produced,when an unusually high forward potential voltage pulse in the order ofseveral kilovolts occurs across a kenotron, it is possible for thekenotron to generate soft X-rays under such conditions. When kenotronsare used as the high voltage rectifying elements of an electricalprecipitator system, then during arcing or sparking of the precipitator,such high voltage potentials are momentarily produced across thekenotrons, with the consequent production of X-rays. Since these burstsof radiation are obviously related to the arcing conditions intheprecipitator, it is an object of the invention to utilize this radiationto measure and ultimately to control the arcing of the precipitator. Inaccordance with the invention, this is accomplished by locating asuitable detecting device, such as a Geiger counter, adjacent thekenotron rectifiers and utilizing the output of the detection device tomeasure and control the input voltage to the precipitator transformerand thus regulate the precipitator voltage in ac cordance with arcingconditions.

In a preferred form of the invention, a Geiger counter is employed asdescribed above, and its output compared 2,783,388 Patented Feb. 26,1957 with the output of a similar Geiger counter exposed to such as aquantity of radioactive material. Uranium is very suitable for thispurpose because of its long half-life, but any other suitableradioactive material having similar characteristics may be employed.

The specific nature of the invention as well as other objects andadvantages thereof will clearly appear from a description of a preferredembodiment as shown in the accompanying drawing, in which:

Fig. 1 is a schematic circuit diagram of a precipitator embodying theinvention; and

Fig. 2 is a schematic diagram of an alternative form of sensing andcircuit controlling arrangement in ac cordance with the invention. I

Referring to Fig. 1, the precipitator is conventionally indicated ashaving a discharge electrode 2, and collector electrode 4, supplied withhigh tension energizing voltage by means of step-up transformer 6connected to the precipitator electrodes through a full wave rectifyingarrangement of four kenotron rectifiers 8, 10, 12, and 14. Thisarrangement is, of course, well known, and need not be described infurther detail. The transformer voltage may be regulated by any suitabledevice, shown, by way of example, as induction regulator 16, which maybe a commercially available Powerstat. The regulator may be driven byany suitable control device such as a motor 18 which may be selectivelydriven in either direction, depending upon which of its opposing fields20 and 22 is energized. Supply terminals 24 are connected to anysuitable power source for this purpose. It will be ap parent that withthe connections shown, if the circuit is closed between point Y andpoint Z, winding 20 will be energized and the motor will be driven inone direc tion, while if the circuit is closed between points Y and X,winding 22 will be energized and the motor will be driven in theopposite direction. In this way, the voltage supplied to theprecipitator can be either raised or lowered, depending upon closure ofthe control circuit between point Y and points X and Z respectively. Afurther variable resistor 26 is preferably provided for supplyingballast; this will also have an effect in determining the intensity ofthe precipitator arcs.

A Geiger counter 28 is placed adjacent any one of kenotrons 814, oralternatively, any two kenotrons of opposite polarity such as 8 and 14are so located that both of them will be equally adjacent to counter 28.As pre viously explained, arcing in the precipitator will produceradiations in the form of X-rays from the kenotrons. The intensity ofthese radiations will obviously effect and determine the output ofGeiger counter 23, so that this output will be related to and a functionof the precipitator arcing. A second Geiger counter 30 is provided, anda suitable source of constant radiation intensity 32 is so locatedadjacent counter 30 that the latter sees a constant amount of radiationfrom the source. The two counters 30 and 28 are oppositely connected tothe same direct current energization source indicated as transformer 34and rectifier 36 with a conventional filter circuit 37. As the output ofa Geiger counter is normally a succession of pulses whose rate isdetermined by the intensity of the radiation to which the counter issubjected, suitable identical pulse charging condenser circuitsindicated at 38 and 40 are provided for the respective Geiger counters,so that the Geiger counter output to the respective grid of tubes 42'and44 are two respective control voltages which are functions of theradiation intensity to which the two as shown to control the output ofthe standard against which the precipitator arcing is measured; thus byad justing counter 30, the desired amount of precipitator arcing can bepreset from zero to several hundred arcs per minute. This adjustment mayalso be made by adjusting the size of the ionizing material or itsdistance from the counter 30.

The respective outputs of tubes 42 and 44 are passed through coils 52and 54 which act oppositely upon armature 56 to control the position ofswitch 58 and thereby determine where the point Y will be connected topoint X or point Z, or neither of them. The latter condition will obtainwhen the currents in coils 52 and 54 are balanced, and the formercondition will obtain when an unbalance exists, that is, the output ofeither tube is greater than that of the other. If the coils 52 and 54are suitably designed, they may also serve to integrate the pulses inthe circuit, and thus provide a measurement or, rather, a comparison, ofthe average pulsing rates in the two circuits.

Another comparison arrangement is shown in Fig. 2. This may be connectedto points X, Y and Z in Fig. 1 in place of the comparison arrangementshown in Fig. 1. Similar elements to those in Fig. l have the samereference number with a prime added. In this case, the outputs of therespective Geiger counters are directly connected to the grids of theirassociated vacuum tubes 42' and 44' as before, and are'also crossconnected by a capacity coupling 62 and 64 to the plates of the oppositevacuum tube. In this manner, a tri-stable multivibrator action isobtained, whereby when the outputs of the two Geiger counters are nearlyequal, the system will oscillate at a period determinted by theconstants of the multivibrator circuit, with very little plate output tothe coils 52 and 54'. This represents the condition wherein point Y isnot connected to either points X or Z. When one or the other Geigeroutputs increases with respect to its opposite, its associated tubebecomes continuously conducting, while the opposite tube is cut olf.Thus monostable operation is produced as is necessary for proper controlof the servo motor circuits.

It will be apparent that many other arrangements could be used toproduce the desired result of comparing the outputs of the two Geigercounters and operating a switchcontrolling circuit in accordance withtheir relative outputs.

Also, other X-ray detecting and measuring devices than Geiger counterscould be used to sense the X-rays produced by the kenotrons. Detectingdevices which are sensitive to radiation other than X-rays should, ofcourse, be suitably shielded from such other radiation which may bepresent.

Although it is an advantage of the present invention that it utilizes aphenomenon normally inherent in the operation of one of the standardelements of an electrical precipitator, namely, the kenotron rectifiers,it will be apparent that in a system employing mechanical rectification,the advantages of the present invention can also be obtained byinserting a kenotron arbitrarily into the system to produce X-rays as afunction of precipitator 4 arcing. It will be noted that the utility ofthe above described principle is not restricted to precipitators, butthat the principle of utilizing X-ray production of kenetron-typerectifiers may be usefully employed in any circuit for the detection orcontrol of high voltage transient conditions.

It will be apparent that the embodiments shown are only exemplary andthat various modifications can be made in construction and arrangementwithin the scope of my invention as defined in the appended claims.

I claim:

1. An electrical precipitator control system comprising a step-uphigh-voltage transformer, a high-voltage vacuum tube rectifier in thesecondary circuit of said transformer, said rectifier having theproperty of emitting X-rays under over-voltage conditions, an electricalprecipitator supplied by said high-voltage rectifier, variable controlmeans for controlling the voltage of said transformer, electricaldetecting means for detecting X-rays produced by said rectifier andproducing an electrical output in accordance therewith, and servo meansfor controlling said variable control means in accordance with theoutput of said detector means.

2. The invention according to claim 1, wherein said electrical detectingmeans comprises means for comparing the intensity of said X-rays withthe intensity of radiation from a standard radioactive source.

3. The invention according to claim 2, wherein said comparing meanscomprises a Geiger counter responsive to the output of said rectifier, asecond Geiger counter responsive to the radiation from said radioactivestandard source, and comparison means associated with said counters forproducing an output in accordance with the difference in outputs of saidcounters.

4. In an electrical precipitator, precipitator electrodes, a step-uptransformer, a rectifier system comprising at least two oppositelyconnected kenotron type thermionic rectifier-s for supplying rectifiedhigh potential from said transformer to said precipitator electrodes,adjustable regulator means for controlling the output of saidtransformer, a Geiger counter located adjacent at least one of saidkenotron type thermionic rectifiers, and servo means controlled by theoutput of said Geiger counter for adjusting said adjustable regulatormeans in accordance with said output.

5. The invention in accordance with claim 4, including a second Geigercounter, a standard source of radioactivity adjacent said second Geigercounter, and circuit means combining the outputs of said Geiger countersin opposition, said circuit means being connected to said servo means.

Ser. No. 376,930, Peycelon et al. (A. P. 0), published May 25, 1943.

